Shielding system for vapor-converters.



L. E. FROST.

SHIELDING SYSTEM FOR VAPOR CONVERTERS.

APPLICATHON FILED Aus.9.19ss.

1,23 1 ,592 Patented J ulj 3, 1917.

WITNESSES: INVENTOR mg 5. 9m

UNITED STATES PATEN OFFICE.

LESLIE E. FROST, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

SHIELDING SYSTEM FOR VAPOR-CONVERTERS.

Specification of Letters Patent.

Patented J nly 3, 1917.

Application filed August 9, 1915. Serial No. 44,413.

To (171 101mm it may concern.

Be it known that I, LESLIE E. From, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have. invented a new and useful Improvement in Shielding Systems for Vaper-Converters, of which the following is a specification.

My invention relates to shielding systems for vapor converters, and it has for its object to provide means that shall minimize short circniting and reverse arcing and oth-- erwise improve the operation in apparatus of the character indicated.

In the accompanying drawing, Figure l is a side view, partially in elevation and partially in section, of a vapor converter embodying the preferred form of my invention; and Fig. 2 is a sectional view of the converter shown in Fig. 1, the section plane being indicated by a line IIII.

In the operation of vapor converters and similar evacuated electric apparatus, current is. in general, conveyed between the electrodes by a stream of negative electrons, emitted by the cathode and proceeding to the anode. The stream of electrons at the cathode may beexcited by any of several -well known methods, chief among which are the maintenance of a keep-alive are to the cathode, the maintenance of the cathode at incandescence, the impact of a stream of positive ions thereagainst, and the impact of a beam of ultra-violet light.

If, in its passage from the cathode to an anode, a negative electron collides with a particle of residual gas, the particle is broken up into a positive ion and a negative electron, both bodies receiving an initial impulse toward the anode by the impact. The newly freed negative electron moves on very rapidly because the propelling force of the electrostatic field is substantially coincident in direction with the initial impulse thus given, but the newly freed positive ion moves but slowly and may soon come to rest and even reverse its direction of movement because of the neutralizing influence of the electrostatic field upon the initial impulse. Furthermore, the acceleration tending to be imparted to the positive ion by the electrostatic field is much less than that of the negative electron because of' the vastly larger mass of the former, although carrying an equal charge. The delivery of a glancing blow to a gas particle by a negative electron may disrupt the particle and force the resultant bodies more or loss transversely to the arc path into comparatively weak fields of electrostatic force.

The passage of an anode to a condition of negative polarity with respect to the cathode, such as happens periodically in a vapor converter, finds a large number of free positive ions afloat in and near the arc path without any well defined motion in any direction. These tramp ions are now attracted to the temporarily negative anode and, if in sufiicient number and sufficiently accelerated, they may bombard the electrode so energetically as to break down the negativeelectrode reluctance thereof, causing short circuiting or reverse arcing Within the apparatus. This harmful action is especially liable to take place if the positive ions impinge upon a globule of mercury or other foreignanatter upon the electrode surface. By my invention, 1 provide means and apparatus whereby these tramp ions are effectually suppressed or neutralized, thus preventing the above described harmful operation.

Referring to the accompanying drawing for a more detailedunderstanding of my invention, 1 show the container of a vapor converter of the metal-case type at 3. The container 3 is provided with a pair of solid anodes 4: and 5 and with a cathode 6, preferably composed of vaporizable conducting material, such, for example, as mercury or suitable amalgams. The anodes 4 and 5 are connected, respectively, to the terminals of asource of alternating current 7, and the cathode 6 is connected to the mid point of the source 7 through a load 8, as is customary in rectifier systems. The cathode 6 is maintained in an active state by a keepalive anode 9 projecting through and insulated from the cover and maintained at a definite positive voltage with respect to the cathode 6 by a suitable unidirectional source 10.

A shielding hood 11 of any desired form is provided for each of the anodes 4 and 5, and supporting members 12 and 13 depend from the lower portions thereof. Transverse plates 141 are supported by, and insulated from, the members 12 and 13, and, in turn, support a large vertically disposed conducting plate 15 which extends entirely potential source which will maintain it at a positive potential with respect to the cathode 6. The keep-alive source is suited for this purpose and I may accordingly connect the plate 15 to the keep-alive anode 9 by a flexible conductor 16, the ,kcep-alive electrode!) being so oflF-set at its lower end as to dispose the keep-alive cathode spot directly beneath the edge of the plate, thus insuring symmetric operation of the two main anodes.

Having thus described the structure of a vapor converter embodying my invention, the operation is as follows: \Vhen the anode at is temporarily positive with respect to the cathode 6, a power are flows thereto, resulting in the production of a number of free positive tramp ions. Said positive ions, especially if forced far out of the arc path by the impact of negative electrons, would tend to be drawn to the anode 5, which is, for the time being, negative, and the resultant bombardment of the anode 5 would, in many cases cause the breakdown of its negative-electrode reluctance, with resultant short circuiting of the converter. The presence of the plate 15, charged positively with respect to the cathode 6, prevents this action, the free positive ions being repelled from the neighborhood of the anode which is, for the time being, negative and also shielded from the electrostatic influence thereof.

If it be found that positive ions thus forced to remain in the neighborhood of an anode tend to be drawn to said anode when the latter reverses in polarity, any desired suppressing or deenergizing means therefor may be provided, such, for example, as shown in the copending application of S. W. Farnsworth, Serial No. 44,429, filed Aug. 9, 1915, and assigned to the Westinghouse Electric & Manufacturing Company.

Throughout this description, I have explained the action of my device in accordance with the theory which seems most plausible in view of the present knowledge of the underlying phenomena. I desire it to be distinctly understood, however, that I do not confine myself to such theory of operation, but merely present the same to aid in an understanding of the invention.

While I have shown my invention in its preferred form, it will be obvious to those skilled in the art that it is susceptible of various minor changes and modifications without departing from the spirit thereof and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invention:

1. In an evacuated electric device, the combination with a plurality of anodes, of a cathode, means for starting and maintaining a rectifying arctherebetneen, a conducting shield disposed between said anodes, and means for maintaining said shield at a positive potential with respect to the cathode.

2. In an evacuated electric device, the combination with a plurality of anodes, of a cathode, means for starting and maintaining a rectifying arc therebetween, a conducting shield disposed between said anodes, and means for maintaining said shield at a definite positive potential with respect to the cathode.

3. In an evacuated electric device, the combination with a plurality of anodes, of a cathode, a source of alternating current, connections from said source to said elec trodes, an auxiliary electrode within said device adjacent to said cathode, a source of direct current connected between said auxiliary electrode and said cathode, so as to maintain said electrode positive with respect to said cathode, whereby a rectifying arc may be initiated and maintained within said device, and a conducting shield between said anodes and connected to said auxiliary electrode, whereby said shield is maintained positive with respect to said cathode.

4. In an evacuated electric device, the combination with a plurality of anodes, of a cathode, a source of alternating current, connections from said source to said electrodes, an auxiliary anode within said device adjacent to said cathode, a source of direct current having its positive terminal connected to said auxiliary anode and its negative terminal connected to said cathode, whereby a rectifying arc may be initiated and maintained within said device, and a conducting shield disposed between said anodes and connected to said auxiliary anode, whereby said shield will be maintained positive with respect to said cathode.

In testimony whereof, I have hereunto subscribed my name this 28th day of July 1915.

LESLIE E. FROST. 

